Traction and flotation have always been important issues with farming and construction vehicles. Having a vehicle mounted on track systems typically provides lower ground pressure, better traction and better use of the available power at higher traction. This is particularly important when the vehicle is operated on soft ground condition or when increased traction effort is required.
One of the challenges when fitting a track system in replacement of a wheel is to fit the track system within the available space envelope of the former wheel. Typical track systems, which feature a pivoting motion, tend to interfere with surroundings equipment such as fenders, fuel or oil tanks, vehicle chassis, three point hitches, etc.
One of the drawbacks of existing track systems is the comfort. One of the reasons is that existing track systems typically do not benefit from the suspension provided by the layer of air within the tires.
More specifically, the existing prior art systems typically comprise one pivot point pivotally connecting the frame undercarriage to the final drive. Such prior art configuration typically requires that the main axle of the vehicle comprises bearings adapted to support the loads. In alternative prior art solution, such as inventions discloses in US patent application no. 2014/0125118 A1, see for instance element 5 and 6 at FIG. 3, and U.S. Pat. No. 5,899,542, for instance elements 22 and 26 at FIG. 1, a fixed attachment surrounds the sprocket wheel. In such configuration, the support frame or undercarriage is pivotally connected to the fixed attachment using two different pivot point, on each lateral side of the sprocket wheel. In yet another prior art document, U.S. Pat. No. 7,201,242, more particularly FIGS. 4A and 5, the track system is connected to a shaft transmitting power. The shaft comprises bearings to allow supporting load of the axle. The shaft is configured to pass through the sprocket wheel to allow rotation of the undercarriage in-between 2 points on both side of the sprocket wheel.
Also, existing prior art also discloses the use of a split frame, as taught in U.S. Pat. No. 5,452,949 or by Class Terra-Trac system. Such prior art track system comprises a split frame having at least two (2) different pivots point, typically a front secondary pivoting assembly which rotates around the vehicle axle attachment and a rear secondary pivoting assembly which rotates around the front secondary pivoting assembly.
The US patent application no. 2014/0125118 discloses a track system comprising a suspension. The dampening system is attached between a support frame surrounding a sprocket wheel. The suspension system comprises two shock absorbers (19 and 20 of FIG. 1) installed at each extremity of the support frame. The said support frame is pivotally connected to the wheels using multiple pivot points.
Prior art also provide longitudinal movement control systems using elastomeric material, such as US patent application published under no. 2007/0029871 or U.S. Pat. No. 8,083,242. Such prior art disclose solution to limit the movement of longitudinal pivoting movement of support wheels and idler wheels. However, these documents do not provide solution to control lateral movement using elastomeric material system.
Hence, there is a need for track systems which can preferably offer most if not all the advantages of track propulsion while fitting in the space envelop of the wheels they replace. Furthermore, there is a need to optimize the existing track system geometry in order to reduce vibration and to provide comfort level higher or at least equal than the level of comfort found in vehicles using tires.